What’s the difference between trash bags, garbage bags and can liners?

In reality, they all refer to same product. The use of one term over the other simply depends on who you are. If you're a homeowner, you likely use the term "trash bags", or "garbage bags", while major companies and industrial institutions tend to use "can liners". Interestingly, in Great Britain trash bags are referred to "bin bags" or "bin liners".